Digital passive electromagnetic pen with pressure detection, control method and device, and storage medium

Abstract

The application provides a digital passive electromagnetic pen with pressure detection, a control method and device, and a storage medium. An LC resonance module receives a wireless carrier signal provided by an electromagnetic digitizer in a pressure communication window to extract electric energy. A differential transformer type displacement sensor converts axial displacement of a pen tip into a differential voltage signal according to a calibration curve. A microcontroller collects the differential voltage signal through an analog-to-digital converter (ADC) and converts the differential voltage signal into pressure level data. A digital modulation module loads the pressure level data into the LC resonance module in a frequency shift keying digital modulation mode and returns the pressure level data to the electromagnetic digitizer, so that high-precision, temperature drift-resistant, tilt angle-resistant, and "pen drop" risk-free pen tip pressure detection is realized under the condition of passive power supply limitation.

Description

Technical Field

[0001] This application belongs to the field of computer input device technology, and particularly relates to a digital passive electromagnetic pen with pressure detection, a control method, a device and a storage medium. Background Technology

[0002] Electromagnetic handwriting input devices have been widely used in computer peripherals such as drawing tablets, handwriting tablets, and signature tablets. Existing passive electromagnetic pens (i.e., pens without batteries, relying on electromagnetic fields emitted by the digitizer for power) are mainly divided into two categories based on their signal processing methods: analog electromagnetic pens and digital electromagnetic pens.

[0003] Traditional analog electromagnetic pens typically employ the following technical solution: the pen does not contain a battery or an MCU (microcontroller). It relies on the pen tip pressing down to compress an elastic element, changing the inductance of the LC resonant circuit inside the pen, thereby causing a resonant frequency or phase shift. The digitizing board detects the amplitude or phase angle change of the feedback signal to infer the magnitude of the pressure.

[0004] However, the aforementioned existing technical solutions have the following significant drawbacks: First, temperature drift leads to inaccurate pressure sensitivity measurement. Second, pen tilt introduces nonlinear errors. Third, the pressure sensitivity sampling time is limited, making it difficult to eliminate pen jitter at the start of the stroke.

[0005] Therefore, there is an urgent need in this field for a new pen tip pressure detection solution to address the above-mentioned technical deficiencies.

[0006] The foregoing statements are for informational purposes only and are not intended to provide background information in connection with this application. Unless otherwise stated herein, the content described in this section is not prior art to the rest of this application. Summary of the Invention

[0007] This invention proposes a digital passive electromagnetic pen with pressure detection, a control method, a device, and a storage medium to overcome at least some of the defects of the prior art. By integrating a differential transformer displacement sensor, an MCU, and a power management module into the passive electromagnetic pen, the pressure signal is digitally acquired and preprocessed locally at the pen tip, and then transmitted back to the digitizing board using frequency shift keying digital modulation. The digitizing board only performs digital demodulation and coordinate packaging, forming a closed-loop architecture of "digital pressure measurement at the pen tip + collaborative verification at the board." This enables high-precision, temperature-drift-resistant, tilt-resistant, and pen-drop-free pen tip pressure detection under conditions of limited passive power supply.

[0008] A further objective of this invention is to achieve pressure-sensitive output under passive power conditions by introducing a ratio-based LVDT demodulation algorithm, dynamic energy balance scheduling, and nonlinear mapping based on the Weber-Fechner law, while simultaneously eliminating temperature drift, tilt error, and pen-starting jitter.

[0009] According to a first aspect of the embodiments of this application, a digital passive electromagnetic pen with pressure detection is provided, comprising:

[0010] pen; The pen tip is movably located at one end of the pen barrel, and the pen tip is displaced along the axis of the pen barrel due to pressure; The LC resonant module is used to receive the wireless carrier signal provided by the electromagnetic digitizer within the pressure communication window to extract electrical energy. A differential transformer displacement sensor has a moving iron core that is mechanically linked to the pen tip to convert the axial displacement of the pen tip into a differential voltage signal according to a calibration curve. The microcontroller acquires the differential voltage signal through an analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data. The digital modulation module is used to load the pressure sensitivity level data into the LC resonant module and transmit it back to the electromagnetic digitizer.

[0011] In some embodiments of this application, an electromagnetic digitizing board electromagnetically coupled to the electromagnetic pen is also included; the electromagnetic digitizing board and the digital passive electromagnetic pen adopt a time-division windowed power supply mechanism, and the wireless carrier signal is alternately transmitted by timing switching between the coordinate scanning window and the pressure communication window. During the coordinate scanning time window, the electromagnetic digitizing board emits the first electromagnetic signal for coordinate positioning, and the MCU control unit of the digital passive electromagnetic pen is in a sleep or power-off state. Within the pressure communication time window, the electromagnetic digitizing board emits a second electromagnetic signal for power supply and synchronization. The MCU control unit of the digital passive electromagnetic pen is awakened and performs sampling of pen tip displacement and feedback of pressure sensitivity level data.

[0012] In some embodiments of this application, the electromagnetic digitizer includes: Antenna array, used to transmit electromagnetic carrier waves and receive the reverse transmission data from the electromagnetic pen; The demodulation unit is used to demodulate the FSK modulated signal received by the antenna array and extract the pressure sensitivity level data; The coordinate positioning unit is used to calculate the coordinate information of the digital passive electromagnetic pen based on the electromagnetic signals received by the antenna array.

[0013] In some embodiments of this application, the microcontroller includes an analog-to-digital converter (ADC); converting differential voltage signals into pressure sensitivity level data includes: The differential voltage signal is acquired by an analog-to-digital converter (ADC) and converted into the ADC's raw digital value. The differential voltage signal is converted into pressure sensitivity level data based on the pre-stored calibration mapping relationship.

[0014] In some embodiments of this application, the pre-stored calibration mapping relationship includes the factory calibration curve and the perceptual nonlinear mapping algorithm; The factory calibration curve is obtained through multi-point pressure calibration, which maps the original digital value of the ADC to a physical pressure value. The perception nonlinear mapping algorithm is based on the Weber-Fechner law and maps physical pressure values ​​to pressure sensitivity level data. The mathematical expression for the perceptual nonlinear mapping algorithm is: ; in, The normalized physical pressure value is given, and α is the sensitivity adjustment coefficient. This represents the maximum pressure sensitivity output level.

[0015] In some embodiments of this application, the signal processing of the differential transformer displacement sensor employs a ratio-based demodulation algorithm, and the MCU control unit calculates the digital displacement quantity. The formula is: ; in, V 1 and V 2 represents the differential output voltage across the secondary coil of the LVDT displacement sensor. K These are the conversion coefficients of the analog-to-digital converter (ADC).

[0016] In some embodiments of this application, the modulation parameters of the digital modulation module satisfy: center frequency fc Matching the resonant frequency of the LC resonant circuit; Modulation index of digital modulation module h satisfy: ; in, R b For the reverse data transmission rate, Δ f This is frequency offset.

[0017] According to a second aspect of the embodiments of this application, a control method for a digital passive electromagnetic pen is provided, comprising: The tip of the electromagnetic pen is displaced along the axis of the pen barrel due to pressure. The LC resonant module receives the wireless carrier signal provided by the electromagnetic digitizing board within the pressure communication window to extract electrical energy. The differential transformer displacement sensor converts the axial displacement of the pen tip into a differential voltage signal according to the calibration curve; the moving iron core of the displacement sensor is mechanically linked to the pen tip. The microcontroller acquires the differential voltage signal through an analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data; The digital modulation module loads the pressure sensitivity level data into the LC resonant module and transmits it back to the electromagnetic digitizer.

[0018] According to a third aspect of the embodiments of this application, a digital passive electromagnetic device with pressure detection is provided, including a memory and a processor; The memory is used to store executable instructions; The processor is used to connect to the memory to execute executable instructions to complete the above-described control method for the digital passive electromagnetic pen.

[0019] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided having a computer program stored thereon; the computer program is executed by a processor to implement a control method for a digital passive electromagnetic pen.

[0020] The present application discloses a pressure-detecting digital passive electromagnetic pen, control method, device, and storage medium. An LC resonant module receives a wireless carrier signal provided by an electromagnetic digitizing board within a pressure communication window to extract electrical energy. A differential transformer displacement sensor converts the axial displacement of the pen tip into a differential voltage signal according to a calibration curve. A microcontroller acquires the differential voltage signal via an analog-to-digital converter (ADC) and converts it into pressure sensitivity level data. A digital modulation module loads the pressure sensitivity level data into the LC resonant module and transmits it back to the electromagnetic digitizing board using frequency-shift keying (FSK) digital modulation.

[0021] This application integrates a differential transformer displacement sensor (LVDT), an MCU, and a power management module into a passive electromagnetic pen. The pen locally performs digital acquisition and preprocessing of pressure signals (ADC sampling, nonlinear mapping), and then transmits the signals back to the digitizing board using frequency shift keying (FSK) digital modulation. The digitizing board only performs digital demodulation and coordinate packaging, thereby realizing a closed-loop architecture of "pen-end digital pressure measurement + board-end collaborative verification".

[0022] Compared with the prior art, the present invention has the following beneficial effects: First, it offers high pressure sensitivity. This invention employs an LVDT displacement sensor, which significantly improves accuracy compared to traditional LC resonant simulation schemes.

[0023] Second, it resists temperature / tilt drift. This invention employs an LVDT ratio demodulation algorithm, where the pressure value is calculated using the normalized ratio of the differential voltage. Common-mode components caused by temperature changes and power supply fluctuations are synchronously canceled out during the division operation. The measured common-mode rejection ratio (CMRR) is better than 60dB, and the pressure sensitivity drift caused by temperature is reduced by more than 90% compared to traditional single-ended inductor solutions. Simultaneously, the pressure value is digitally transmitted back at the pen tip, no longer relying on the LC resonant phase angle to simulate offset; tilt angle changes do not affect the pressure sensitivity curve.

[0024] Third, the sampling rate does not decrease or the pen drops under passive conditions. This invention adopts a windowed power supply and dynamic energy balance scheduling strategy. During the board-end coordinate scanning, the MCU inside the pen is not powered. The MCU is only awakened to work during the pressure communication window, and the overall power consumption is controllable. When the voltage of the energy storage capacitor is insufficient, the system automatically reduces the accuracy to maintain the connection, fundamentally eliminating the "pen dropping" phenomenon caused by the excessively long sampling time of high-order pressure sensitivity in traditional solutions.

[0025] Fourth, no jitter at the start of the stroke. This invention integrates a sliding window median filtering algorithm into the MCU at the pen tip, which can complete the sorting of sampled values, outlier removal, and median output within the wake-up window, greatly eliminating single-pulse interference and achieving "zero-delay stroke start".

[0026] Fifth, the human-computer interaction experience has been optimized. This invention introduces a nonlinear logarithmic mapping based on the Weber-Fechner law, which makes the pressure-sensitive output curve match the characteristics of human tactile perception and the brush response curve of mainstream drawing software such as Photoshop, resulting in sensitive strokes, stable pressure, and a natural drawing feel. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 The diagram shows a schematic of a pressure-detecting digital passive electromagnetic pen according to an embodiment of this application. Figure 2 The diagram shows an overall architecture block diagram of a pressure-detecting digital passive electromagnetic pen and digitizer device according to an embodiment of this application; Figure 3 The diagram shows the correspondence between the windowed power supply timing of the electromagnetic digitizing board and the working state of the pen-end MCU during a complete frame scan cycle according to an embodiment of this application. Figure 4 The diagram shows a step-by-step schematic of a control method for a digital passive electromagnetic pen according to an embodiment of this application; Figure 5 A flowchart illustrating another digital passive electromagnetic pen control method provided in an embodiment of the present invention; Figure 6 The diagram shows a structural schematic of a digital passive electromagnetic device with pressure detection according to an embodiment of this application. Detailed Implementation

[0028] Regarding this application, traditional analog electromagnetic pens typically do not have an internal battery or MCU (microcontroller). They rely on the pen tip pressing down to compress an elastic element, changing the inductance of the internal LC resonant circuit, thereby causing a resonant frequency or phase shift. The digitizing board detects the amplitude or phase angle change of the feedback signal to infer the magnitude of the pressure applied. The existing technology has the following significant drawbacks: First, temperature drift leads to inaccurate pressure sensitivity measurements. Since pressure sensitivity measurement relies entirely on the analog offset calculation of LC resonant parameters, the inductance is easily affected by temperature drift. Actual tests show that pressure sensitivity can fluctuate by approximately 30% between 0°C and room temperature, severely impacting user experience and drawing accuracy.

[0029] Second, pen tilt introduces non-linear errors. When the electromagnetic pen is tilted, the mechanical transmission path of the pen tip undergoes non-linear deformation. The larger the tilt angle, the more significant the pressure sensitivity error, resulting in inconsistent pressure output under different pen grip postures.

[0030] Third, the pressure sampling time is limited, making it difficult to eliminate pen-start jitter. The digitizer needs to complete coordinate and pressure calculations within the transmit / receive interleaved scanning window, and the time available for pressure sampling within the reporting cycle is extremely limited, making it difficult to effectively filter out jitter at the moment of pen start.

[0031] Furthermore, existing technologies, such as a digital electromagnetic pen, use a pen-end MCU for local ADC sampling and transmit pressure data via amplitude modulation. However, this approach relies on an "energy indicator beacon" for amplitude calibration, and the strength of the pen-end signal is significantly affected by the working height, resulting in insufficient anti-interference capability. Another example is a digital electromagnetic pen system that uses a capacitive pressure sensor to measure pressure through charge-discharge timing. However, in this approach, the counter timing relies on the LC resonant frequency (approximately 500kHz). To achieve 8192 levels of pressure sensitivity, the charge-discharge timing duration needs to be more than 16 milliseconds, causing a "pen drop" phenomenon when the electromagnetic pen is slid rapidly. Yet another example is the existing technology that uses magnetic core displacement to change inductance to detect pressure. However, these technologies all use a single-ended inductor structure, making the output signal susceptible to common-mode interference from temperature and supply voltage. Moreover, they require a second frequency-to-voltage conversion before being sent to the ADC, resulting in significant accumulated errors.

[0032] Therefore, there is an urgent need in this field for a pen tip pressure detection solution that can achieve high precision, resistance to temperature drift, resistance to tilt angle, and no risk of "pen dropping" under conditions of limited passive power supply.

[0033] The purpose of this application is to overcome at least some of the defects of the prior art and to provide a digital passive electromagnetic pen and digitizer device with a pressure detection module.

[0034] The more specific purpose of this application is to integrate a differential transformer displacement sensor (LVDT), an MCU, and a power management module into a passive electromagnetic pen. The pen locally completes the digital acquisition and preprocessing of pressure signals (ADC sampling, nonlinear mapping), and then transmits them back to the digitizing board using frequency shift keying (FSK) digital modulation. The digitizing board only performs digital demodulation and coordinate packaging, thereby realizing a closed-loop architecture of "pen-end digital pressure measurement + board-end collaborative verification".

[0035] The further objective of this application is to achieve 16K level pressure-sensitive output under passive power conditions by introducing a ratio-based LVDT demodulation algorithm, dynamic energy balance scheduling, nonlinear mapping based on the Weber-Fechner law, and median filtering of the pen tip sliding window, while eliminating temperature drift, tilt error, and pen start jitter.

[0036] The present application discloses a pressure-detecting digital passive electromagnetic pen, control method, device, and storage medium. It extracts electrical energy by receiving a wireless carrier signal provided by an electromagnetic digitizing board within a pressure communication window via an LC resonant module. A differential transformer displacement sensor converts the axial displacement of the pen tip into a differential voltage signal according to a calibration curve. A microcontroller acquires the differential voltage signal via an analog-to-digital converter (ADC) and converts it into pressure sensitivity level data. A digital modulation module loads the pressure sensitivity level data into the LC resonant module and transmits it back to the electromagnetic digitizing board using frequency-shift keying digital modulation.

[0037] This application integrates a differential transformer displacement sensor (LVDT), an MCU, and a power management module into a passive electromagnetic pen. The pen locally performs digital acquisition and preprocessing of pressure signals (ADC sampling, nonlinear mapping), and then transmits the signals back to the digitizing board using frequency shift keying (FSK) digital modulation. The digitizing board only performs digital demodulation and coordinate packaging, thereby realizing a closed-loop architecture of "pen-end digital pressure measurement + board-end collaborative verification".

[0038] To make the technical solutions and advantages of the embodiments of this application clearer, the exemplary embodiments of this application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0039] Example 1 Figure 1 The diagram shows a schematic of a pressure-detecting digital passive electromagnetic pen according to an embodiment of this application.

[0040] like Figure 1 As shown, a digital passive electromagnetic pen with pressure detection in this embodiment includes: The pen barrel 10 and the pen tip 11 are movably disposed at one end of the pen barrel 10. The pen tip 11 is displaced along the axial direction of the pen barrel due to pressure.

[0041] The LC resonant module 20 is used to receive the wireless carrier signal provided by the electromagnetic digitizing board within the pressure communication window to extract electrical energy; and to provide a reverse load modulation communication path for the electromagnetic digitizing board.

[0042] The differential transformer displacement sensor 30 (LVDT) is mechanically linked to the pen tip 11 by the moving iron core of the displacement sensor 20, and is used to convert the axial displacement of the pen tip into a differential voltage signal according to the calibration curve.

[0043] Microcontroller 40 (MCU) acquires the differential voltage signal via analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data. Microcontroller 30 is activated within the pressure communication window.

[0044] The digital modulation module 50 is used to load pressure sensitivity level data into the LC resonant module 20 and transmit it back to the electromagnetic digitizing board using frequency shift keying (FSK) digital modulation.

[0045] The pen body is equipped with modules such as LC resonant module 20, differential transformer displacement sensor 30, microcontroller 40 and digital modulation module 50. The internal modules are connected to the pen tip 11 through the pen barrel 10.

[0046] In this case, the electromagnetic digitizing board stops supplying power to the MCU of the digital passive electromagnetic pen within the coordinate scanning window, and only wakes up the MCU to work within the pressure communication window.

[0047] In the preferred implementation process, an electromagnetic digitizing board electromagnetically coupled to the electromagnetic pen is also included; the electromagnetic digitizing board and the digital passive electromagnetic pen adopt a time-division windowed power supply mechanism, and the wireless carrier signal is alternately transmitted by switching between the coordinate scanning window and the pressure communication window.

[0048] Specifically, within the coordinate scanning time window, the electromagnetic digitizing board emits the first electromagnetic signal for coordinate positioning, while the MCU control unit of the digital passive electromagnetic pen is in a sleep or power-off state.

[0049] Within the pressure communication time window, the electromagnetic digitizing board emits a second electromagnetic signal for power supply and synchronization. The MCU control unit of the digital passive electromagnetic pen is awakened and performs sampling of pen tip displacement and feedback of pressure sensitivity level data.

[0050] In the preferred implementation process, the electromagnetic digitizer includes: Antenna array, used to transmit electromagnetic carrier waves and receive the reverse transmission data from the electromagnetic pen; The demodulation unit is used to demodulate the FSK modulated signal received by the antenna array and extract the pressure sensitivity level data; The coordinate positioning unit is used to calculate the coordinate information of the digital passive electromagnetic pen based on the electromagnetic signals received by the antenna array.

[0051] In the preferred implementation, the microcontroller 40 includes an analog-to-digital converter (ADC); the process of converting the differential voltage signal into pressure-sensitivity level data includes: first, acquiring the differential voltage signal through the ADC and converting it into the ADC's raw digital quantity; then, converting the differential voltage signal into pressure-sensitivity level data according to a pre-stored calibration mapping relationship.

[0052] In the preferred implementation process, the pre-stored calibration mapping relationships include the factory calibration curve and the perception nonlinear mapping algorithm.

[0053] Among them, the factory calibration curve is obtained through multi-point pressure calibration, which maps the original digital value of the ADC to the physical pressure value.

[0054] Among them, the perception nonlinear mapping algorithm is based on the Weber-Fechner law, which maps physical pressure values ​​to pressure sensitivity level data.

[0055] The mathematical expression for the perceptual nonlinear mapping algorithm is: ; in, The normalized physical pressure value is α, which is the sensitivity adjustment coefficient (α ranges from 10 to 50). This is the maximum pressure sensitivity output level (16384 levels).

[0056] In the preferred implementation process, the signal processing of the differential transformer displacement sensor adopts a ratio demodulation algorithm, and the MCU control unit calculates the digital displacement quantity. The formula is: ; in, V 1 and V 2 represents the differential output voltage across the secondary coil of the LVDT displacement sensor. K This represents the conversion coefficient of the analog-to-digital converter (ADC). This ratio-based demodulation is used to compensate for common-mode interference caused by temperature variations and electromagnetic field fluctuations.

[0057] In the preferred implementation process, the modulation parameters of the digital modulation module 50 satisfy: center frequency fc It matches the resonant frequency of the LC resonant circuit.

[0058] Modulation index of digital modulation module h satisfy: ; in, R b For the reverse data transmission rate, Δf Frequency offset. Frequency offset Δ f The preferred setting is 3% to 6% of the carrier frequency to balance the low power consumption of the digital passive electromagnetic pen with the frequency discrimination resolution of the electromagnetic digitizer demodulation unit.

[0059] In the preferred implementation process, the calibration curve of the differential transformer displacement sensor is fixed in the Flash memory of the microcontroller through a factory calibration process; the factory calibration process includes: 1. Apply multiple standard pressure points with progressively increasing pressure to the pen tip using standard weights; 2. Record the raw ADC value corresponding to each standard pressure point; 3. The least squares method is used to perform polynomial fitting between the standard pressure point and the original ADC value to generate calibration curve coefficients and store them in Flash. 4. The digital passive electromagnetic pen reads the calibration curve coefficients directly from the Flash memory during operation and maps the ADC sampling values ​​to physical pressure values ​​in real time.

[0060] In the preferred implementation process, the digital passive electromagnetic pen also includes an energy storage capacitor and a voltage monitoring module; The MCU control unit executes a dynamic energy balance adaptive sampling strategy based on the voltage value of the energy storage capacitor detected by the voltage monitoring module. When the voltage value is higher than the first threshold, the ADC analog-to-digital conversion module performs sampling at 14-bit full resolution and outputs the highest pressure sensitivity level. When the voltage value is lower than the first threshold but higher than the second threshold, the ADC analog-to-digital conversion module automatically reduces the frequency to 10-bit resolution sampling and outputs the secondary high voltage level to prioritize ensuring the continuity of data transmission. When the voltage value is lower than the second threshold, the MCU control unit is forced into deep sleep, stops sampling and transmission, and waits for the carrier power supply in the next pressure communication time window.

[0061] In the preferred implementation, the resonant frequency of the LC resonant circuit is matched with the electromagnetic carrier frequency emitted by the electromagnetic digitizing board, and the electromagnetic carrier frequency range is 400kHz ~ 600kHz. When the FSK modulation unit performs reverse data transmission, the resonant frequency is changed by connecting or disconnecting capacitors of different capacitance values ​​in parallel on the LC resonant circuit to achieve binary frequency shift keying. The energy consumption of this modulation method is lower than that of the analog amplitude modulation method.

[0062] In the preferred implementation process, in the time-sharing windowed power supply mechanism, the pressure communication time window and the coordinate scanning time window are sequentially continuous and do not overlap; Within the pressure communication time window, the electromagnetic signal emitted by the electromagnetic digitizing board contains a synchronization head. After the MCU control unit of the digital passive electromagnetic pen detects the synchronization head, it starts sampling the pen tip displacement and FSK reverse data transmission.

[0063] In the preferred implementation process, the electromagnetic digitizing tablet and the digital passive electromagnetic pen adopt a half-duplex communication protocol, which includes two data structures: long frames and short frames. The long frame contains a frame start delimiter and a 5-byte address field, while the short frame contains a frame start delimiter and a 1-byte address field.

[0064] Preferably, the delimiter of the long frame is 0x82, which is used by the master device to send complete address information containing the manufacturer ID (MfgID), device type (DevType), and device ID (DevID) to the slave device.

[0065] The timing parameters for half-duplex communication transmission and reception switching include: the setup time from the falling edge of the Request to Send (RTS) to the carrier reaching its first peak; and the shutdown delay from the carrier removal to the falling edge of the carrier detection (CD) signal.

[0066] In the preferred implementation process, within a complete frame scan cycle of the electromagnetic digitizing board, the single-window emission excitation duration of the coordinate scanning window is configured to be 20μs to 80μs, and the inter-window sleep duration of the pressure communication window is configured to be 100μs to 500μs.

[0067] Within the pressure communication window, the MCU is woken up and performs a complete pressure sampling and FSK feedback with a total activation time of 30μs to 60μs to ensure that all operations are completed within the sleep period.

[0068] Preferably, the selection parameters for the differential transformer displacement sensor (LVDT) meet the following requirements: Measurement range: ±0.1mm to ±500mm, preferably, the micro-displacement range for precision handwriting input is ±1mm; Linearity: better than 0.1%FS (full scale); Sensitivity: Adaptable to ADC range, output signal sensitivity is 50mV / mm to 200mV / mm; Excitation parameters: The primary coil is provided with a low-distortion sine AC excitation source by an external or internal conditioning module, with an excitation voltage of 3Vrms or 6.3Vrms and an excitation frequency of 2.5kHz or 5kHz.

[0069] Figure 2 The diagram shows an overall architecture block diagram of a pressure-detecting digital passive electromagnetic pen and digitizer according to an embodiment of this application.

[0070] like Figure 2As shown, the device includes an electromagnetic digitizing board 200 and a passive digital electromagnetic pen 100. The electromagnetic digitizing board 200 includes a main control MCU 206, a transmitting circuit module 204, an analog switch module 202, a drive circuit module 203, an antenna array 201, and a digital demodulation module 205. The passive digital electromagnetic pen 100 includes an LC resonant module (inductor + capacitor), a power management circuit (including an LDO regulator and a voltage monitoring module), an energy storage capacitor, an MCU chip, and an LVDT displacement sensor.

[0071] Figure 3 The diagram shows the correspondence between the windowed power supply timing of the electromagnetic digitizing board and the working state of the pen-end MCU during a complete frame scan cycle according to an embodiment of this application.

[0072] like Figure 3 As shown in the figure, the horizontal axis represents time, and the vertical axis from top to bottom represents: the digitizer's transmitting state, the pen tip's LC resonant power-drawing state, the pen tip's MCU operating state, and the voltage change trend of the energy storage capacitor. Within a complete frame scan cycle T_frame (approximately 15ms), the following alternate sequentially appear: coordinate scan window (T_tx=60μs), inter-window sleep (T_sleep=300μs), and pressure communication window (T_act=45μs).

[0073] A pressure-detecting digital passive electromagnetic pen according to this application includes: a pen barrel; a pen tip movably disposed at one end of the pen barrel, the pen tip being displaced along the axial direction of the pen barrel due to pressure; an LC resonant module for receiving a wireless carrier signal provided by an electromagnetic digitizing board within a pressure communication window to extract electrical energy; a differential transformer-type displacement sensor, the moving iron core of the displacement sensor being mechanically linked with the pen tip, for converting the axial displacement of the pen tip into a differential voltage signal according to a calibration curve; a microcontroller for acquiring the differential voltage signal through an analog-to-digital converter (ADC) and converting the differential voltage signal into pressure sensitivity level data; and a digital modulation module for loading the pressure sensitivity level data onto the LC resonant module and transmitting it back to the electromagnetic digitizing board.

[0074] This application integrates a differential transformer displacement sensor (LVDT), an MCU, and a power management module into a passive electromagnetic pen. The pen locally performs digital acquisition and preprocessing of pressure signals (ADC sampling, nonlinear mapping), and then transmits the signals back to the digitizing board using frequency shift keying (FSK) digital modulation. The digitizing board only performs digital demodulation and coordinate packaging, thereby realizing a closed-loop architecture of "pen-end digital pressure measurement + board-end collaborative verification".

[0075] A further objective of this invention is to achieve pressure-sensitive output under passive power conditions by introducing a ratio-based LVDT demodulation algorithm, dynamic energy balance scheduling, and nonlinear mapping based on the Weber-Fechner law, while simultaneously eliminating temperature drift, tilt error, and pen-starting jitter.

[0076] Compared with the prior art, the present invention has the following beneficial effects: First, it offers high pressure sensitivity. This invention employs an LVDT displacement sensor, which significantly improves accuracy compared to traditional LC resonant simulation schemes.

[0077] Second, it resists temperature / tilt drift. This invention employs an LVDT ratio demodulation algorithm, where the pressure value is calculated using the normalized ratio of the differential voltage. Common-mode components caused by temperature changes and power supply fluctuations are synchronously canceled out during the division operation. The measured common-mode rejection ratio (CMRR) is better than 60dB, and the pressure sensitivity drift caused by temperature is reduced by more than 90% compared to traditional single-ended inductor solutions. Simultaneously, the pressure value is digitally transmitted back at the pen tip, no longer relying on the LC resonant phase angle to simulate offset; tilt angle changes do not affect the pressure sensitivity curve.

[0078] Third, the sampling rate does not decrease or the pen drops under passive conditions. This invention adopts a windowed power supply and dynamic energy balance scheduling strategy. During the board-end coordinate scanning, the MCU inside the pen is not powered. The MCU is only awakened to work during the pressure communication window, and the overall power consumption is controllable. When the voltage of the energy storage capacitor is insufficient, the system automatically reduces the accuracy to maintain the connection, fundamentally eliminating the "pen dropping" phenomenon caused by the excessively long sampling time of high-order pressure sensitivity in traditional solutions.

[0079] Fourth, no jitter at the start of the stroke. This invention integrates a sliding window median filtering algorithm into the MCU at the pen tip, which can complete the sorting of sampled values, outlier removal, and median output within the wake-up window, greatly eliminating single-pulse interference and achieving "zero-delay stroke start".

[0080] Fifth, the human-computer interaction experience has been optimized. This invention introduces a nonlinear logarithmic mapping based on the Weber-Fechner law, which makes the pressure-sensitive output curve match the characteristics of human tactile perception and the brush response curve of mainstream drawing software such as Photoshop, resulting in sensitive strokes, stable pressure, and a natural drawing feel.

[0081] Example 2 This application also provides a control method for a digital passive electromagnetic pen. For details not disclosed in the control method of the digital passive electromagnetic pen in this embodiment, please refer to the specific implementation of the digital passive electromagnetic pen and device with pressure detection in other embodiments.

[0082] Figure 4 The diagram illustrates the steps of a control method for a digital passive electromagnetic pen according to an embodiment of this application.

[0083] like Figure 4 As shown, a control method for a digital passive electromagnetic pen includes the following steps: S1: The tip of the electromagnetic pen is displaced along the axis of the pen barrel due to pressure. S2: The LC resonant module receives the wireless carrier signal provided by the electromagnetic digitizer within the pressure communication window to extract electrical energy; and provides a reverse load modulation communication path for the electromagnetic digitizer. S3: The differential transformer displacement sensor converts the axial displacement of the pen tip into a differential voltage signal according to the calibration curve; the moving iron core of the displacement sensor is mechanically linked with the pen tip to measure the displacement of the pen tip; S4: The microcontroller acquires the differential voltage signal through the analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data; the microcontroller (MCU) is woken up within the pressure communication window; S5: The digital modulation module loads the pressure sensitivity level data into the LC resonant module and transmits it back to the electromagnetic digitizer using frequency shift keying (FSK) digital modulation.

[0084] Figure 5 The overall flowchart of another digital passive electromagnetic pen control method provided in the embodiment of the present invention is shown.

[0085] like Figure 5 The control method of this application embodiment is further illustrated below: I. Timing-based launch steps.

[0086] The electromagnetic digitizing board alternately transmits wireless carrier signals in a time-division multiplexing manner, dividing a complete frame scanning cycle into a coordinate scanning window and a pressure communication window. Within the coordinate scanning window, the electromagnetic digitizing board transmits scanning carriers for coordinate positioning; within the pressure communication window, the electromagnetic digitizing board transmits communication carriers containing synchronization signals.

[0087] II. Passive power supply and sleep mode procedures.

[0088] The LC resonant module of the digital passive electromagnetic pen receives wireless carrier signals and extracts electrical energy to charge the energy storage capacitor; during the coordinate scanning window, the electromagnetic digitizing board stops providing wake-up signals to the microcontroller (MCU) of the digital passive electromagnetic pen, and the MCU remains in a deep sleep state or a power-off state. III. Wake-up and displacement detection steps.

[0089] When the electromagnetic digit tablet switches to the pressure communication window, it sends a synchronization wake-up signal to the digital passive electromagnetic pen. The MCU of the digital passive electromagnetic pen is awakened by the synchronous wake-up signal, which activates the differential transformer displacement sensor (LVDT). The moving iron core of the LVDT generates axial displacement with the pressure of the pen tip and converts the displacement into a differential voltage signal output.

[0090] IV. Local digital sampling steps.

[0091] The MCU's built-in analog-to-digital converter (ADC) samples the differential voltage signal during the active duration TactTact of the pressure communication window to generate the raw digital pressure value.

[0092] V. Data Processing and Mapping Steps.

[0093] The MCU maps the original digital pressure value to the physical pressure value based on the calibration curve pre-stored in the Flash memory, and performs a non-linear logarithmic mapping on the physical pressure value to generate the final pressure level data.

[0094] VI. Digital modulation and return transmission steps.

[0095] The MCU transmits the final pressure level data to the electromagnetic digitizing board in reverse by controlling the load impedance change of the LC resonant module through frequency shift keying (FSK) digital modulation.

[0096] VII. Demodulation and Output Steps.

[0097] The electromagnetic digitizing board receives the reverse radiation signal within the pressure communication window, digitally demodulates the FSK signal, extracts the final pressure level data, packages the final pressure level data with the current coordinate data, and uploads it to the host computer.

[0098] The present application proposes a control method for a digital passive electromagnetic pen with pressure detection. The passive electromagnetic pen integrates a differential transformer displacement sensor (LVDT), an MCU, and a power management module. The pressure signal is digitally acquired and preprocessed locally at the pen tip (ADC sampling, nonlinear mapping), and then transmitted back to the digitizing board using frequency shift keying (FSK) digital modulation. The digitizing board only performs digital demodulation and coordinate packaging, thereby realizing a closed-loop architecture of "digital pressure measurement at the pen tip + collaborative verification at the board tip".

[0099] Example 3 This embodiment provides a digital passive electromagnetic device with pressure detection. For details not disclosed in this embodiment, please refer to the specific implementation details of digital passive electromagnetic systems or methods with pressure detection in other embodiments.

[0100] Figure 6 The diagram shows a structural schematic of a digital passive electromagnetic device with pressure detection according to an embodiment of this application.

[0101] like Figure 6 As shown, the digital passive electromagnetic device 410 with pressure detection includes: a storage unit 402 for storing executable instructions; and a processing unit 401 for connecting to the storage unit 402 to execute the executable instructions to complete the control method of the digital passive electromagnetic pen with pressure detection.

[0102] Those skilled in the art will understand that the illustration Figure 6 This is merely an example of a pressure-sensing digital passive electromagnetic device 410 and does not constitute a limitation on the pressure-sensing digital passive electromagnetic device 410. It may include more or fewer components than shown, or combine certain components, or different components. For example, the pressure-sensing digital passive electromagnetic device 410 may also include input / output devices, network access devices, buses, etc.

[0103] The processing unit 401 (Central Processing Unit, CPU) can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processing unit 401 can be any conventional processor. The processing unit 401 is the control center of the pressure-detecting digital passive electromagnetic device 410, connecting all parts of the pressure-detecting digital passive electromagnetic device 410 via various interfaces and lines.

[0104] Storage unit 402 can be used to store computer-readable instructions. Processing unit 401 implements various functions of the pressure-detecting digital passive electromagnetic device 410 by running or executing the computer-readable instructions or modules stored in storage unit 402 and calling the data stored in storage unit 402. Storage unit 402 may mainly include a program storage area and a data storage area. The program storage area may store the operating system, application programs required for at least one function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created according to the use of the pressure-detecting digital passive electromagnetic device 410, etc. In addition, storage unit 402 may include hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, read-only memory (ROM), random access memory (RAM), or other non-volatile / volatile storage devices.

[0105] If the integrated module of the pressure-detecting digital passive electromagnetic device 410 is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of the present invention can also be implemented by instructing related hardware through computer-readable instructions. These computer-readable instructions can be stored in a computer-readable storage medium, and when executed by a processor, they can implement the steps of the various method embodiments described above.

[0106] Example 4 This embodiment provides a computer-readable storage medium having a computer program stored thereon; the computer program is executed by a processor to implement the control method of a pressure-detecting digital passive electromagnetic pen in other embodiments.

[0107] In summary, the pressure-detecting digital passive electromagnetic device and storage medium of this application receive the wireless carrier signal provided by the electromagnetic digitizing board within the pressure communication window through the LC resonant module to extract electrical energy; the differential transformer displacement sensor converts the axial displacement of the pen tip into a differential voltage signal according to the calibration curve; the microcontroller acquires the differential voltage signal through the analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data; the digital modulation module loads the pressure sensitivity level data into the LC resonant module and transmits it back to the electromagnetic digitizing board using frequency shift keying digital modulation.

[0108] Those skilled in the art will understand that the terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “an,” and “the” as used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0109] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0110] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0111] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A digital passive electromagnetic pen with pressure detection, characterized in that, include: pen; The pen tip is movably mounted at one end of the pen barrel, and the pen tip is displaced along the axial direction of the pen barrel due to pressure; The LC resonant module is used to receive the wireless carrier signal provided by the electromagnetic digitizer within the pressure communication window to extract electrical energy. A differential transformer displacement sensor, wherein the moving iron core of the displacement sensor is mechanically linked with the pen tip to measure the displacement of the pen tip, and is used to convert the displacement of the pen tip into a differential voltage signal according to a calibration curve; The microcontroller acquires the differential voltage signal through an analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data. A digital modulation module is used to load the pressure sensitivity level data into the LC resonant module and transmit it back to the electromagnetic digitizing board.

2. The digital passive electromagnetic pen according to claim 1, characterized in that, It also includes an electromagnetic digitizing board that is electromagnetically coupled to the electromagnetic pen; the electromagnetic digitizing board and the digital passive electromagnetic pen adopt a time-division windowed power supply mechanism, and alternately transmit wireless carrier signals by switching between the coordinate scanning window and the pressure communication window in a time sequence. During the coordinate scanning time window, the electromagnetic digitizing board emits a first electromagnetic signal for coordinate positioning, and the MCU control unit of the digital passive electromagnetic pen is in a sleep or power-off state. Within the pressure communication time window, the electromagnetic digitizing board emits a second electromagnetic signal for power supply and synchronization, and the MCU control unit of the digital passive electromagnetic pen is awakened to perform the sampling of the pen tip displacement and the feedback of the pressure sensitivity level data.

3. The digital passive electromagnetic pen according to claim 2, characterized in that, The electromagnetic digitizing tablet includes: An antenna array is used to transmit the electromagnetic carrier wave and receive the reverse transmission data from the electromagnetic pen; The demodulation unit is used to demodulate the FSK modulated signal received by the antenna array and extract the pressure sensitivity level data; The coordinate positioning unit is used to calculate the coordinate information of the digital passive electromagnetic pen based on the electromagnetic signals received by the antenna array.

4. The digital passive electromagnetic pen according to claim 1, characterized in that, The microcontroller includes an analog-to-digital converter (ADC); the conversion of the differential voltage signal into pressure sensitivity level data includes: The differential voltage signal is acquired by the analog-to-digital converter (ADC) and converted into the ADC's raw digital quantity; The differential voltage signal is converted into pressure sensitivity level data according to the pre-stored calibration mapping relationship.

5. The digital passive electromagnetic pen according to claim 4, characterized in that, The pre-stored calibration mapping relationship includes the factory calibration curve and the perception nonlinear mapping algorithm; The factory calibration curve is obtained through multi-point pressure calibration, which maps the original digital value of the ADC to a physical pressure value. The perception nonlinear mapping algorithm is based on the Weber-Fechner law and maps the physical pressure value to the pressure sensitivity level data. The mathematical expression for the perceptual nonlinear mapping algorithm is: ； in, The normalized physical pressure value is given, and α is the sensitivity adjustment coefficient. This represents the maximum pressure sensitivity output level.

6. The digital passive electromagnetic pen according to claim 4, characterized in that, The signal processing of the differential transformer displacement sensor employs a ratio-based demodulation algorithm, and the MCU control unit calculates the digital displacement value. The formula is: ； in, V 1 and V 2 represents the differential output voltage across the secondary coil of the LVDT displacement sensor. K These are the conversion coefficients of the analog-to-digital converter (ADC).

7. The digital passive electromagnetic pen according to claim 1, characterized in that, The modulation parameters of the digital modulation module satisfy: center frequency fc Matching the resonant frequency of the LC resonant circuit; The modulation index of the digital modulation module h satisfy: ； in, R b For the reverse data transmission rate, Δ f This is frequency offset.

8. A method based on claim 1 The control method for the digital passive electromagnetic pen according to any one of the seven claims is characterized in that, include: The tip of the electromagnetic pen is displaced along the axis of the pen barrel due to pressure. The LC resonant module receives the wireless carrier signal provided by the electromagnetic digitizing board within the pressure communication window to extract electrical energy. The differential transformer displacement sensor converts the displacement of the pen tip into a differential voltage signal according to the calibration curve; the moving iron core of the displacement sensor is mechanically linked with the pen tip to measure the displacement of the pen tip; The microcontroller acquires the differential voltage signal through an analog-to-digital converter (ADC) and converts the differential voltage signal into pressure sensitivity level data; The digital modulation module loads the pressure sensitivity level data into the LC resonant module and transmits it back to the electromagnetic digitizing board.

9. A digital passive electromagnetic device with pressure detection, characterized in that, Including memory and processor; The memory is used to store executable instructions; The processor is configured to connect to a memory to execute executable instructions to perform the control method for the digital passive electromagnetic pen as described in claim 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program is executed by the processor to implement the control method of the digital passive electromagnetic pen as described in claim 8.

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